The present disclosure relates to a magnetic circuit and a key input device.
In recent years, reduction in thickness of a key input device such as keyboards has been developed. For example, a key input device provided with rubber domes and scissor mechanism is mainly used in a personal computer (PC) keyboard. In such a key input device, when a user presses a keytop horizontally supported by the scissor mechanism, the keytop depresses the rubber dome, and then an electrical connection is made in a membrane sheet circuit and an input signal is transmitted.
In general, rubber domes can be manufactured cost-effectively, and thus it is possible to manufacture the key input device at low cost. However, there is a limit to further reduction in thickness of the rubber dome and scissor mechanism. As an example, a further reduction in thickness of the rubber dome causes a key-depression feeling given to a user when pressing a keytop to make worse due to deterioration of the buckling characteristic of the rubber dome (this feeling will be referred to hereinafter as “click feeling”) and it becomes unclear if the keytop is pressed. In addition, for example, a further reduction in thickness of the scissor mechanism will cause the strength thereof to be reduced and thus the durability thereof will be impaired.
Thus, there has been proposed a method of using a magnetic attraction force or attractive force acting between a pair of magnets (or between a magnet and a magnetic body such as metal pieces) without using the buckling characteristic of the rubber dome (for example, refer to U.S. Patent Application Publication No. 2012/0169603). When this method (using a magnetic force) is applied to the key input device, it is possible to use a magnetic attraction force or attractive force acting between a pair of magnets (or between a magnet and a magnetic body such as metal pieces) as a force for maintaining a keytop in position. Thus, it is possible to achieve further reduction in thickness of the key input device while suppressing the deterioration of a click feeling given to the user.